Gelatin obtained in the later extractions (beyond 15 weight % of the bone) from an alkaline processed ossein is typically high in color (absorbance at 420 nm), low in Gel Strength, and high in viscosity. Low Gel strength limits the applicability of the gelatin in imaging, and some pharmaceutical and edible applications where enhanced setting properties of gelatin are necessary.
The extraction of gelatin from collagen-bearing materials such as ossein is typically performed in tanks with a perforated false bottom. The ossein rests on the false bottom in a bed and water is introduced into the bed at temperatures of from 120 to 180.degree. F. The ossein is steeped in the heated water for one to four hours, then the gelatin solution is removed from the vessel, with the ossein retained in the vessel on the false bottom. Fresh water at a higher temperature is introduced into the vessel, and a second extraction cycle begins. In other cases, the gelatin solution is continuously drained and fresh hot water is added to the vessel in order to maintain the liquid level. A charge of ossein typically undergoes several of these extraction cycles at increasing temperatures or prolonged extraction at gradually increasing temperature. As a result of the higher extraction temperatures, and the increasing level of impurities in the remaining ossein, gelatins produced from the later extractions are less transparent and darker in color than gelatin from earlier extractions, and are less valuable for photographic purposes.
After extraction of photographic gelatin from ossein, the remaining ossein can be heated to the boiling point to solubilize the remaining gelatin. This extracted gelatin has a low Gel strength, typically 60-120 Bloom grams and is unsuitable for photographic applications.
An object of the invention is to provide a gelatin of photographic quality from the residual ossein.
Another object of the present invention is to provide a process for recovering high quality gelatin from the residual ossein.